Thanks. However something is still wrong. I think if I did this, I should have the image left upper corner at the middle of the screen, which doesn’t happen.
FVector2D newSize(1920.0f/2.0f * 1920.0f / ViewportSize.X, 1080.0f / 2.0f * 1080.0f / ViewportSize.Y);
imageSlot->SetPosition(newSize);
But thanks anyway!